THERMAL CONTROL SUBSYSTEM

Transcription

1 THERMAL CONTROL SUBSYSTEM Thermal Mission PDR Jeff Asher Los Angeles, California February 12, 2015 Thermal-1 MPDR, 2/12/2015

2 SUBSYSTEM TEAM Name Jeff Asher Ken Shrivastava Renee Krieger Chris Knapp Responsibility Lead Thermal Engineer Thermal Model Analysis Thermal Model Production Thermal Requirements Thermal-2 MPDR, 2/12/2015

3 OUTLINE 1. Thermal Design Philosophy 2. Requirements 3. Temperature Limits and Approach 4. Thermal Modeling Tools and Design Inputs 5. Thermal Analysis and Results 6. Trade Studies 7. Schedule 8. Risks 9. Peer PDR RFAs Thermal-3 MPDR, 2/12/2015

4 Thermal Isolation Military Relevance Isolate vulnerable spacecraft components Relies on thermally resistant materials (e.g. Delrin or PEEK) Passive Control Methods External Coatings Kapton and Silvered Teflon coatings are being considered to augment the optical properties of the exterior of the spacecraft Active Control Methods GENERAL PROTECTION PLAN Operational Control As a contingency, attach resistive heaters to components that may fail to remain within operational temperature bounds Modeling Simulate the thermal environment onboard using of steadily increasing fidelity Testing Utilize testing facilities in order to validate model Thermal-4 MPDR, 2/12/2015

5 Past modeling efforts carried out by student based MatLab code named ARIEN - Discontinued Modeling has continued through the use of Thermal Desktop The team is currently working on two models Over-simplified Model Substitutes an aluminum box for the internal components Currently being used for preliminary results Simple Model MODELING APPROACH Uses TD solids and surfaces to define components onboard Conduction is still in development The goal: To finish development of the Simple Model and begin generating results The results from the Simple Model will be compare with that of the Over Simplified Model to ensure results are in agreement Continuous improvement will be made to the Simple Model until components are able to be accurately modeled and results can be verified Thermal-5 MPDR, 2/12/2015

6 THERMAL TESTING APPROACH We plan on utilizing our thermal vacuum chamber to perform tests to help validate our model Tests will be conducted to create an environment that can be replicated by Thermal Desktop in order to correlate results We will measure temperature differences at joints using several thermocouples to accurately model conductors We can then recreate the thermal vacuum chamber s environment in Thermal Desktop and verify the temperatures of points heat and transfer across nodes The spacecraft will not be powered on for testing Heaters can be used to replicate heat loads Thermal-6 MPDR, 2/12/2015

7 THERMAL REQUIREMENTS REQ ID Requirement Rationale Parent(s) Verification Method Temperature sensors shall be installed Allows for diagnostics THRM 01 within the CubeSat and be accessible during of potential thermal UNP NS8 I: Inspection thermal testing whether the CubeSat is issues during testing Userguide (p.62) powered on or not. and operations Components need to THRM 02 be at a certain A/T: Thermal analysis; The spacecraft TCS shall keep all bus temperature to SYS 30 Verified during Thermal components within operating temperatures operate within Vacuum Testing specification. THRM 03 THRM 04 THRM 05 The spacecraft TCS shall keep all bus components within survival temperatures The spacecraft TCS shall not exceed the mass allocated by Systems The spacecraft TCS shall not exceed the power allocated in the ELFIN system power budget Components need to be at a certain temperature to prevent any damage to that component. Limited spacecraft mass available for thermal control Limited spacecraft power available for thermal control SYS 29 SYS 14 SYS 22 A/T: Thermal analysis; Verified during Thermal Vacuum Testing I: Components will be weighed A/T: Measured power consumption data during component tests Allocated Mass: 4g Allocated Power: 0W Thermal-7 MPDR, 2/12/2015

8 TEST/MODELING LIMIT APPROACH Manufacturer set as qualification level by default If impractical, we will discuss components on a case by case basis Thermal Goal is set with 5 C of margin from operational limits Thermal-8 MPDR, 2/12/2015

9 ELFIN THERMISTORS LOCATIONS IDPU PRM SMAR Batteries Radio EPD Sensor Not Pictured: Panels, Fluxgate Magnetometer Tuna Can SBPCB Thermal-9 MPDR, 2/12/2015

10 THERMAL ANALYSIS TOOLS - THERMAL DESKTOP Thermal Desktop is an extension to AutoCAD Has the ability to accurately model heat transfer due to conduction, convection, and radiation Finite Element Method calculations are built into the software and more reliable than student based code Thermal-10 MPDR, 2/12/2015

11 A CLOSER LOOK Thermal-11 MPDR, 2/12/2015

12 Orbit Parameters: Polar Orbit i = 90 ORBIT ANALYSIS Altitude = 800km Eccentricity = 0 Beta Angle precesses causing different orbit scenarios Dawn-Dusk Orbit Determined as absolute hot case scenario Constant solar radiation on one side of spacecraft Thermal-12 MPDR, 2/12/2015

13 ORBIT ANALYSIS Noon-Midnight Orbit Determined cold case scenario Rotisserie Motion scenario Thermal-13 MPDR, 2/12/2015

14 Over-simplified Model consists of Chassis Panels Solar Cells Internal component box Models internal components as a single aluminum block THERMAL ANALYSIS AND RESULTS 14 Thermal-14 MPDR, 2/12/2015

15 HOT CASE Dawn Dusk Orbit w/ Nominal Heat load(2.2w) Thermal-15 MPDR, 2/12/2015

16 HOT CASE Dawn Dusk W/o Heat load (Safety Mode) Thermal-16 MPDR, 2/12/2015

17 COLD CASE Noon Midnight w/ Nominal Heat load(2.2 W) Thermal-17 MPDR, 2/12/2015

18 COLD CASE Noon Midnight Orbit w/o Power Load (Safety Mode) Thermal-18 MPDR, 2/12/2015

19 PRELIMINARY RESULTS Operating Temps Storage Temps Dawn Dusk w/ power Dawn Dusk w/o power Noon Midnight w/ Power Noon Midnight w/o power Min Max Min Max Min Max Min Max Min Max Min Max Panels Solar Cells Internal Components Components in green satisfy 5 C margin with operational limits Components in yellow do not satisfy margin requirement but are within Survivable limits Components in red do not satisfy 5 C margin of Survivable limits Thermal-19 MPDR, 2/12/2015

20 POINTS OF INTEREST The internal components (defined by the batteries temperature limits) require significant attention and thermal mitigation Components are reaching extremely hot and cold temperatures The thermal environment on board ELFIN needs to stabilize the environment on board Thermal-20 MPDR, 2/12/2015

21 FGM Protection Protect isolated scientific instrument and provide a stable thermal environment Compressed MLI vs. Aluminum Tape External Coating Cold biasing the spacecraft with reflective coatings 5 mil Aluminized Kapton EPD Radiator Dedicated radiator space on the +X and/or Z panel using surface treatments Isolate EPD s from the rest of bus through use of MLI blankets and insulated standoff blocks Battery Protection Plan CURRENT TRADE STUDIES Isolating the batteries thermally in order to achieve challenging charging requirements Thermal-21 MPDR, 2/12/2015

22 SCHEDULE Task Name Start Finish Thermal Mon 8/25/14 Tue 6/2/16 Thermal Documentation Mon 8/25/14 Tue 6/2/16 Developing Spacecraft Thermal Model Wed 10/1/14 Mon 5/18/15 Create Simple Model Wed 10/1/14 Mon 1/5/15 Results Mon 1/5/15 Fri 2/13/15 Comparison & Validation Mon 2/16/15 Fri 5/8/15 Develop Simple Model Mon 1/5/15 Fri 3/13/15 Preliminary Results Fri 3/13/15 Wed 4/1/15 Modeling Conductance Mon 1/5/15 Fri 3/13/15 Port Solid Works to AutoCAD Wed 10/1/14 Fri 12/12/14 Add Internal Heat Generation Mon 2/16/15 Fri 3/13/15 Variable Beta Analysis Mon 3/16/15 Fri 5/8/15 Thermal Desktop Model Mon 3/16/15 Mon 5/18/15 Thermal Transient Analysis Mon 3/16/15 Fri 4/24/15 Spacecraft Bus Thermal Mitigation Strategies Mon 12/1/14 Fri 6/2/15 Model Batteries Fri 3/13/15 Wed 4/1/15 Model Stacer (?) Mon 3/16/15 Fri 3/27/15 Model Radio (?) Mon 3/16/15 Fri 3/27/15 Design Protection Scheme Batteries Thu 4/2/15 Wed 4/8/15 Design Protection Scheme Radio Mon 3/30/15 Fri 4/3/15 Design Protection Scheme Solar Cells (?) Mon 3/16/15 Fri 3/20/15 Instrument Thermal Mon 12/1/14 Thu 7/12/15 Model FGM Mon 1/12/15 Fri 3/13/15 Model EPD Mon 3/16/15 Fri 3/27/15 Design Protection Scheme FGM Mon 3/30/15 Fri 5/29/15 Design Protection Scheme EPD Mon 3/30/15 Fri 5/29/15 Thermal-22 MPDR, 2/12/2015

23 RISKS Significant risk is introduced by trusting the team s development and implementation of the thermal model Risks Team experience Challenging requirements (EPD vs. Battery) Passive thermal design requires careful implementation and testing Risk mitigation strategy Extensive testing in the thermal vacuum chamber Professional mentorship for the thermal team Thermal-23 MPDR, 2/12/2015

24 PEER PDR REVIEW BOARD MEMBERS Name Organization Specialty Chris Smith Keith Novak Nickolas Emis UCB JPL JPL Thermal Modeling and Design Thermal Modeling and Design Thermal Modeling and Design RFAs: Develop simple test plans to validate thermal model early Analyze thermally isolating the batteries and EPD s Integrate transient power values into model Coordinate with power subsystem to track all energy dissipation throughout the satellite Analyze different beta angles, orbits, and orientations to determine sensitivities Model EPD s and Stacer Chute as heat traps Thermal-24 MPDR, 2/12/2015